With all shuttle
and experiment systems operating in fine fashion, the five member
STS-93 crew aboard Columbia will be busy again this evening with a variety
of secondary experiments.

Commander Eileen Collins, Pilot
Jeff Ashby and Mission Specialists Cady Coleman, Steve Hawley and Michel
Tognini were awakened at 5:31 p.m. CDT with the song “Brave New
Girls," performed by Teresa.

Hawley, the resident astronomer
of the STS-93 crew, will continue his work with the Southwest Ultraviolet
Imaging System, or SWUIS instrument, to collect imagery of targets associated
with Mercury, Venus, Jupiter and the Moon. Although small, the sensitive
SWUIS system has unique attributes that make it a valuable complement
to more expensive space observatories such as the Hubble Space Telescope.
Among these attributes are SWUIS's unusually wide field of view (up
to 30 times Hubble's) and its ability to observe objects much closer
to the Sun than most space observatories. This latter capability allows
SWUIS to explore the inner solar system -- something few other instruments
can do.

Collins and Ashby will be responsible
for maneuvering Columbia in support of various experiments including
observations made with the SWUIS telescope or the Midcourse Space Experiment
(MSX), which uses sophisticated sensors to collect ultraviolet, infrared,
and visible light data of firings of the shuttle’s orbital maneuvering
system engines or primary reaction control system jets.

Collins also will conduct a
conversation with students at the Harbor View Elementary School in Corona
Del Mar, California using the Shuttle Amateur Radio Experiment (SAREX)
system. She also will check experiments associated with the Cell Culture
Module (CCM) and the Biological Research In Canister (BRIC) payloads.

At 4:36 a.m. CDT on Sunday,
Collins and Coleman will conduct an interview with CBS Radio Network.
Coleman also will be interviewed by Donna Shirley, former mission manager
for the Mars Pathfinder Project, in conjunction with the National Endowment
for the Arts’ Mars Millenium Project.

Coleman will work with the
Plant Growth Investigations in Micro-Gravity (PGIM) and the Lightweight
Flexible Solar Array Hinge (LFSAH) experiments, and document on-orbit
operations with High Definition Television (HDTV) equipment.

Ashby will tend to various
orbiter systems and check the Space Tissue Loss (STL) experiment. STL
is a payload designed to validate models of bone and muscle loss induced
by the weightless environment of space.

Tognini will use the SAREX
system to conduct a ham radio conversation with fellow French astronaut
Jean-Pierre Haignere who is currently flying aboard the Russian Mir
Space Station. That communication opportunity is planned for early Sunday
morning at 12:33 a.m. CDT. He'll also help check the BRIC and LFSAH
experiments, and work with experiments in the Commercial Generic Bio-Processing
Apparatus (CGBA).

While the STS-93 crew presses
on with the remainder of its flight, the Chandra X-Ray Observatory team
at the Operations Control Center in Cambridge, Mass., is preparing for
the first burn of Chandra's Integral Propulsion System. The firing is
scheduled for about 8:11 p.m. CDT on Saturday, July 24. Two of Chandra's
four Liquid Apogee Engines will burn for approximately five minutes.
Tonight's burn will be the first of four apogee burns that will result
in an increase to Chandra's perigee. Later in the mission, there will
be one perigee burn to increase the spacecraft's apogee. There are four
engines, two primary and two redundant. Each engine has 105-pounds of
thrust and uses hydrazine as fuel with nitrogen tetroxide as the oxidizer.

Following the first Integral
Propulsion System burn, the new perigee is expected to be 750 miles
(1,200 kilometers) and the new apogee is expected to be 45,014 miles
(72,023 kilometers). Chandra's new orbit duration will be 24 hours,
38 minutes, slightly longer than its current orbit of 24 hours, 17 minutes.

Columbia is orbiting at an
altitude of 158 x 148 nautical miles circling the Earth once every 90
minutes.